A fabrication technique based on molten metal infiltration casting for producing metal matrix composites (MMC) and a technique for reinforcing such composites by use of fibers made of reinforcing materials, such as aluminium oxide, silicon carbide, silicon nitride, boron, graphite, etc., which are incorporated into the metal matrix are known in the relevant art. In the production of metal matrix composites thus reinforced by fibers, parts of various alloys containing from 30 to 60 percent fibers by volume can be fabricated relatively easily. It is known from the well-established rule of mixture that a high content of such fibers can improve the mechanical and physical properties of the fiber-reinforced metal matrix composites.
For successfully reinforcing the metal matrix composite with fibers, it is very important that the reinforcement should have the right content of fibers and be set rigidly at the right location in the cavity of the casting mold. One example for achieving the desired rigidity of the fiber reinforcement is disclosed by Japanese Patent Publication No. 56-111,565 of 1981, according to which reinforcing fiber bundles are immersed in a volatile organic solvent and thereafter shaped into a fiber reinforcement body having a form which suits the mold cavity in which it is to be placed. In a further known proposal disclosed by Japanese Patent Publication No. 56-66,368 of 1981, a yarn of high-strength fibers is wound around an aluminium wire to make a reinforcement string, and a number of such strings are shaped into a reinforcement body having a form which substantially corresponds to that of the casting to be produced.
However, these proposals have a serious disadvantage in that, because the fibers of the reinforcement body when placed in the mold cavity tend to be moved easily, they are very likely to be deflected from their intended location within the cavity by the flow of molten metal as it is being injected into the cavity under pressure, with the result that the strength of the resulting metal matrix composite is decreased, or part of the fibers may be exposed on the product surface. In addition, because fiber reinforcement bodies according to the prior art are made by hand, the fibers cannot be practically arranged with the required uniformity of distribution thereof within the body, and manufacturing of reinforcement bodies on a mass production basis cannot be achieved.